Car Troubles, and I'm Stumped...

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Jpec07

Jpec07

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Forgotten Wing
Hey all,

I know it's been a long time since I've posted here, but I still consider this to be the best knowledge-base around for automotive concerns, and lately, my car's been having some pretty interesting issues. I have yet to call a mechanic about it, but everyone I tell about the problem seems to be just as confused by it as I am.

For the record, I drive a 1988 Nissan Sentra 2-Door Sedan with manual transmission (I don't like automatic anymore--I'm not actually controlling the car with auto tranny). It's still got only 88k miles on it (which checks out on Carfax), and every mechanic who's ever touched it says it's in phenominal shape for an engine so old.

Apparently they haven't seen it recently.

About a week and a half ago, I noticed something off with my thermostat. Usually, it rests at about halfway (normal for most cars after they've been on for a while), but when I first caught it, the orange dial was moving up and up and up on the scale, until I thought the car was about to overheat. Odd thing is that it stops just before that little line it's never supposed to cross, and so I, deciding to play it safe, turn the heat on full blast with AC off and windows down to try and cool the engine off a bit.

Here's where it really gets confusing; not only does the car seem to think it's on the verge of overheating, but the heat is not working. By that, I don't just mean that the heat isn't working to cool the engine down, I mean that the air being pushed through the vents when the heat is full blast is the same temperature as when the slider that controls temperature is all the way cold. It's as though the heating coil or whatever isn't working quite right either. You'd expect the heat going full blast with the engine on the verge of overheating to be hot, right? No such luck. It only ever gets warm if the engine's running particularly close to that line.

Other notes of problems with the car are that the idle seems to be staying at a higher RPM than usual, and that while the car is idling, something squeaks intermittently.

My thoughts on the matter originally were that I just need a thermostat, but then I noticed that the heat wasn't putting out hot air at all. I'm going to check my radiator fluid on Saturday (no time 'til then), and if that doesn't do the trick, take it to a mechanic to get it looked at.

Any ideas as to what it might be?
 
When diagnosing coolant system problems, always check the coolant first.

Then check the cooling fan relay and/or fuses, as those can be faulty or not even plugged in.

I remember when my car was having cooling problems, the idle was inconsistent and it would almost stall. This was due to a faulty coolant temperature sensor, which was not sending the correct engine temperature to the computer. The coolant sensor was telling the computer that the outside temperature was -80 degrees F, which is impossible in SoCal. :lol:

I hope that I helped, cooling problems are most likely electrical and not mechanical. They are also a pain in the 🤬
 
If it's a high pressure coolant system, it could be something as simple as a radiator cap.
 
Sorry, I don't have experience in this yet, but my school book lists possible causes.

High temp gauge reading:
- Trailer being towed, steep hill being climbed, vehicle being operated in slow moving traffic, or engine idling during high ambient temps with A/C on. High altitudes can aggravate these conditions.
- Faulty temp gauge
- Temp warning lamp illuminating unnecessarily
- Low coolant in overflow/reserve tank and radiator
- Pressure cap not installed tightly
- Poor seals at radiator cap
- Coolant low in radiator but not in reserve tank. This means the radiator is not drawing coolant from the coolant reserve tank as the engine cools.
- Freeze point of coolant not correct. Mixture may be rich.
- Coolant not flowing through system
- Radiator or A/C condensor fins are dirty
- Radiator core is plugged or corroded
- Fuel or ignition system problems
- Dragging brakes
- Bug screen is being used, causing reduced airflow
- Thermostat partially or completely shut
- Electric cooling fan not operating properly
- Cylinder head gasket leaking
- Heater core leaking

No heating:
- blown blower fuse
- open blower switch
- bad blower motor
- fan loose on shaft
- open wiring
- inoperative flow valve
 
It sounds like you may have air in the radiator hoses. You should try bleeding out the system. I know whenever I had to change the coolant on my celica bleeding out the system was a gigantic pain, but if not done correctly I had the same problem you are having. NO HOT AIR! Maybe, this wil help?
 
Jpec07
I'm going to check my radiator fluid on Saturday (no time 'til then)
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Are you saying you haven't opened your rad cap yet to see if there's coolant in there? Like Helden said, that should be the first thing you check.

If your coolant is low your engine could overheat, as your temp gauge seems to indicate. Also, your heater won't work very well because heated coolant passing through the heater core is what heats the air in the first place. Low coolant = not much heat from the vents.

Seriously, you should check it before you drive the car anymore, driving with very low coolant can cause serious engine damage. With the engine cool, check the level of coolant in the overflow tank (should be between the MAX and MIN markings), then pop the rad cap and look down inside with a flashlight. You should see coolant in there, if not you should top it up with ~1:1 antifreeze/water mix.
 
Thermostat is malfunctioning, either partially closed or open.

With that set of miles its possible for you to still be on your first cooling system, but those parts can still age with time. My car's 10 year old thermostat decided to close itself shut and blow up my expansion tank. Hopefully on your car and engine its in an easily reachable location because thermostats are a relatively easy and inexpensive fix.
 
I love how some people can diagnose your cars problem without even seeing the car and pronounce, definitively what the cause is.

If you are too time pressed to take a minute, ONE MINUTE, to check your coolant level before you drive your car, perhaps you should be taking the bus. you. are. NOT. that. busy. You've got time to play on the internets and ask questions about your car here.

When diagnosing a problem, you should always start with the simplest and least expensive solutions first. And proceed in a logical and cogent manner.

Check your coolant level. And stop pretending you DONT have the time.
 
I'd be willing to bet your radiator is clogged or your thermostat is stuck closed.
 
Thirdeye
I'd be willing to bet your radiator is clogged or your thermostat is stuck closed.
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I wouldn't.

I'd be willing to bet he's low on coolant or has air trapped in the line. If his thermostat was stuck closed, the car would go from cold to boiling in the first 15 minutes of driving. He's said it never seems to actually overheat. But the bouncing temp gauge is symptomatic of the temp sensor encountering pockets of air within the warm coolant, and a bubble trapped in the wrong place can prevent or restrict the amount of coolant flowing through the heater core.

Sounds like flush-n-fill time to me.

Oh, and at the OP: Don't be an ass about the manual transmission thing. I myself strongly prefer a manual transmission, but I still consider myself as driving and in control when I drive my wife's automatic car.
 
Admittedly, I am very muchso a n00b when it comes to car maintenance. Fortunately my car's got balls of steel, and apparently knows how to handle being a little thirsty.

That's right, my car was basically out of antifreeze/coolant when I opened it up (which Haynes' Repair Manual suggested would take 20-30 minutes with the engine cold - it is a pressurized system, apparently). Filled it up, including the reserve tank, with about a gallon and a half of water, and I've got some antifreeze for when I get a chance to bleed the system so I can have a not dead vehicle again.

Concerns now are leaky hoses and components (which I got some of that Prestone Stop Leak stuff to take care of), and what damage may have been done to the engine while it was in such a volatile state. Anything I should look out for in the long term (besides coolant levels)?

(Oh, and sorry for the asshattedness about manual transmission, most likely won't happen again here. Nice to see you too, though, Duke <_<)
 
Forget the stop leak stuff all it will do is clog up the rest of the system> If you have a leak fix it right (no band-aids) should ever be used to fix a car unless it's a temporary thing until you can get the right part. A good thing to do to check your car for leaks (oil,gas,water,etc) is to take your car and wash the engine area real good then after it dries (run car) so as not to allow the electric system to trap moisture park the car with a large piece of cardboard under it, then the next day look at the cardboard to see if you have any major leaks. Note: Look under car before moving it so if you do have a leak you will know where to look.
Check your fluid levels often.Check tires, brakes, belts, brake fluid, power steering fluid, all lights on car. If you don't know anything or not very much about cars ask for help from someone you know most people will help you out.
 
First thing I was going to suggest was the coolant level, but I guess you found that out already.

Coolant doesn't just dissapear unless there's other problems. Figure out why your coolant went away, Might even be as bad as a blown head gasket.


Let the car warm up until the radiator fan kicks on and the thermostat opens, and if you have white smoke coming out of your exhaust, especially when revving the engine, then you have a blown headgasket.

It can also do the opposite, and blow exhaust fumes into the coolant, in which case the pressure would rise and you could blow a coolant line off, or worse, break something.


Either way, let your car warm up fully, rev it up a little and look for a leak. Make sure your A/C isn't on while you do this, as it also drips water and you don't want anything else leaking at the same time.
 
Also, when you drain the water out in order to add the 50/50 antifreeze mix, look for evidence of oil. Catch it in a pan and look closely at it. It will look like chocolate milk if there is oil in the water. That could likely also mean a blown headgasket.
 
Now, this is going to be an incredibly nerdy question, and it won't make much difference, but are we talking 50% by volume, or 50% by mass? I can distill a container full of antifreeze well enough on my own, I just need to know what we're talking about here.

(lol, jk :P)

Thanks for the tips, guys, and for putting up with my disedumacashun about car maintenance. *nodnod*
 
50% by volume. Take an empty gallon jug from windshield washer fluid and pour half the gallon of antifreeze into it. Fill both jugs with water to the top. Put one in the car, top off the car, and put the rest on the shelf in your garage.
 
I would say either lots of air, or a clog in the cooling system. Either way, I'd say a full system flush is in order. If you know what you're doing, you can pick up a coolant flush kit from an auto parts store. Otherwise, it's kind of a pain in the ass that might be better off with a mechanic.
 
Does the heater work now? It's a common problem for the heater core to block up in older systems, in which case get a professional reverse flush, or go the whole nine yards and replace the heater core (usually involves taking the dash out).

The lesson: check your coolant before starting a thread... :P
 
Jpec07
Concerns now are leaky hoses and components (which I got some of that Prestone Stop Leak stuff to take care of), and what damage may have been done to the engine while it was in such a volatile state. Anything I should look out for in the long term (besides coolant levels)?
Click to expand...
Careful with that stuff if you're planning to leave your car sitting round for a while. About 2 weeks before we went on Holiday our car developed a small radiator leak, the garage put some of this stuff in. While the car was sitting still for 2 weeks in the airport carpark the stuff set and we had to drive 200 miles home with the heating at full blast and the temp gauge scarily high.
 

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